I hope I haven't missed anything but the patch should be the following.
>From acd488c22b4bb2ee42526be8ca67145d5127b014 Mon Sep 17 00:00:00 2001
From: Michal Hocko <mhocko@xxxxxxxx>
Date: Wed, 17 Jun 2020 10:40:47 +0200
Subject: [PATCH] mm: do_swap_page fix up the error code
do_swap_page returns error codes from the VM_FAULT* space. try_charge
might return -ENOMEM, though, and then do_swap_page simply returns 0
which means a success.
We almost never return ENOMEM for GFP_KERNEL single page charge. Except
for async OOM handling (oom_disabled v1). So this needs translation to
VM_FAULT_OOM otherwise the the page fault path will not notify the
userspace and wait for an action.
Fixes: 4c6355b25e8b ("mm: memcontrol: charge swapin pages on instantiation")
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
---
mm/memory.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/mm/memory.c b/mm/memory.c
index dc7f3543b1fd..d944b7946b27 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3140,8 +3140,10 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
err = mem_cgroup_charge(page, vma->vm_mm,
GFP_KERNEL);
ClearPageSwapCache(page);
- if (err)
+ if (err) {
+ err = VM_FAULT_OOM;
goto out_page;
+ }
lru_cache_add(page);
swap_readpage(page, true);
--
2.26.2
--
Michal Hocko
SUSE Labs
